1. Field of the Invention
The present invention relates to a semiconductor device including a lead partially enclosed by a resin material. It also relates to a method of making such a semiconductor device.
2. Description of the Related Art
FIG. 12 of the accompanying drawings shows a conventional semiconductor device. The device, generally indicated by reference sign B, is an 8-segment display unit incorporating eight LED chips in a housing 90. The device B includes a plurality of leads 91 each of which has an outer end portion 92 to surface-mount the device.
The conventional device B is made in the following manner. First, as shown in FIGS. 13A and 13B, a liquefied resin material 93 is poured into the housing 90. Then, as shown in FIG. 13C, the LED chips 94 mounted on the leads 91 are immersed into the resin material 93. The outer end portions 91a of the leads 91 protrude from the resin material 93, and in this state the resin material 93 is hardened. Finally, the outer end portions 91a are subjected to bending and/or cutting procedures, to provide the surface-mounting terminals 92 shown in FIG. 12.
In the above manner, the LED chips 94 can be simply enclosed by resin, so that the production efficiency is advantageously improved. However, the conventional method has found disadvantageous in the following respect.
The leads 91 of the conventional device B are obtained by etching a metal plate 95. Specifically, as shown in FIG. 14A, a resist layer 96 provided with appropriate openings is formed on the upper and the lower surfaces of the plate 95. Then, as shown in FIG. 14B, isotropic etching is performed on the plate 95 from above and below. Since the etching is isotropic, it progresses laterally as well as vertically through the plate 95. Accordingly, the resultant leads 91 are formed, in their side surfaces, with grooves 91c. 
As best shown in FIG. 15, the grooves 91c extend longitudinally of the leads 91. When the thus-grooved leads 91 are put into the resin 93 for executing the step shown in FIG. 13C, the liquefied resin 93 tends to rise along the grooves 91c by capillary action toward the extremity of the outer end portion 91a. As a result, most of the outer end portion 91a may be covered by the resin material, which is disadvantageous to soldering the end portion 91a to e.g. a printed circuit board.
The present invention has been proposed under the circumstances described above. It is, therefore, an object of the present invention to provide a method of fabricating a semiconductor device that does not suffer from the undesired covering of the terminals by the applied resin material in a molten state. Another object of the present invention is to provide a semiconductor device produced by such a method.
According to a first aspect of the present invention, there is provided a fabrication method of a semiconductor device. The method comprises the steps of: preparing a lead including an inner portion and an outer portion; connecting a semiconductor element to the inner portion of the lead; and immersing the semiconductor element and the inner portion of the lead into liquefied resin in a manner such that the outer portion of the lead, as a whole, protrudes from the liquefied resin. The outer portion of the lead is provided with an enlarged part for interrupting the flow of the liquefied resin along the lead, that is caused by the capillary action.
The method of the present invention may further comprise the step of putting the semiconductor element, together with the inner portion of the lead connected to the element, into place within a housing prepared for accommodating the element, the lead, etc.
The method of the present invention may further comprise the step of pouring the liquefied resin into the housing. The order of this resin-pouring step and the above-mentioned element-housing step may be interchangeable.
Preferably, the enlarged part may include a resin-interrupting surface directed toward the liquefied resin in which the semiconductor element and the inner portion of the lead are immersed.
Preferably, the lead may be prepared by etching a metal plate. As a result of the etching process, the lead may be formed with two side surfaces which have been processed by the etchant and are spaced from each other in the width direction of the lead. In this instance, the enlarged part may preferably protrude in the width direction of the lead so that it interrupts the resin flow along the above-mentioned two side surfaces. According to the present invention, the lead may also be prepared by punching a metal plate.
According to a second aspect of the present invention, there is provided a semiconductor device that comprises: a semiconductor element; a housing that accommodates the semiconductor element; a resin material arranged in the housing for enclosing the semiconductor element; and a lead that is connected to the semiconductor element and includes an inner portion embedded in the resin material and an outer portion protruding from the resin material. The outer portion of the lead is provided with an enlarged part including a barrier surface directed toward the resin material arranged in the housing.
Preferably, the outer portion of the lead may include a connection terminal that is farther from the resin material in the housing than the barrier surface is. With this arrangement, the barrier surface prevents the connection terminal from being covered by the resin material in a molten state during the fabrication procedure of the semiconductor device. Preferably, the connection terminal may be smaller in width than the enlarged part.
Preferably, the semiconductor element may be a light-emitting diode (LED), and the housing may be formed with an opening that allows the passage of the light emitted from the LED.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.